When I got done with him, I’m sure he could have fought professionally. He was a natural.” — Jake LaMotta on training ROBERT DE NIRO for “Raging Bull”Everett Collection.

LaMotta strikes a tough pose in 2009. (REUTERS)

On Dec. 19, 1980, Martin Scorsese unleashed “Raging Bull” on theaters. The life story of Bronx-born middleweight champ Jake LaMotta was a searing parable of the American dream, its bloody scenes underscored by striking black-and-white cinematography. Nominated for eight Oscars, including Best Picture, it won Best Actor for Robert De Niro and Best Editing. On Tuesday, the film’s 30th anniversary will be marked by a new Blu-ray edition with 50 minutes of new material, including interviews with Scorsese and De Niro. The Post visited LaMotta, whose autobiography inspired the movie, at his Manhattan apartment, to let the champ, now 89, tell his side of the story.

Marty Scorsese’s a tremendous director. He’s very accurate, and he’s got a purpose behind what he’s doing that only he knows. I can’t say nothing bad about him. We got along very good, and we knew from the beginning this would be something special.

There’s nobody that could have done what De Niro did with this movie. He was very dedicated. I worked with him for about a year before we shot anything. We boxed over a thousand rounds together. At first, he was afraid to hit me. Then I said to him, “Don’t worry about it. You can’t hurt me. I’m used to all these punches.” I gave him confidence that his punches wouldn’t be so bad. Then he went right at it. He changed overnight. I don’t know how he did it, but he got into the mood.

He took a pretty good punch, too, although I never hit him with all my might. But when I banged him around a little bit, he didn’t complain. He just tried harder.

Robert lived every part of it. He studied me. He started to live like me, talk like me, eat like me, walk like me. He asked me a lot of questions. He knew more about me than I did.

When I got done with him, I’m sure he could have fought professionally. He was a natural. He wouldn’t have been a champion, but he could have been rated.

During the shoot, whenever there was a problem, they would call me and ask me my version of what happened. There were little changes in the movie from the book. Scorsese created things as he went along.

The only thing I complained about was too much profanity. I never did like to use profanity with children around the house. But it was good for the movie to overdo it a little bit, to make it come across.

The violence in the film was just — that’s the way I was. I was a bad guy at certain things. My jealousy was true. But my wife, I never hit her, and in the movie he hits her. I threatened to hit her. I yelled at her and all that. There were times I wanted to hit her. But I never did really hit her.

When the movie came out, I became a hero in a way. Even today I went for a walk, and a couple of old-

timers recognized me. I said hello, shook their hands. I became champ all over again. That’s what people say: “How ya doin’, champ.” I like that they call me “champ.”

I was in awe of the whole thing, and I was satisfied with the way they portrayed me. My life story on film. That doesn’t happen to everybody.